From 2f12f03436847e063cda8cc4c339ad84961cbf39 Mon Sep 17 00:00:00 2001 From: Paul Mackerras Date: Mon, 15 Oct 2012 01:17:17 +0000 Subject: [PATCH] KVM: PPC: Book3S HV: Fixes for late-joining threads If a thread in a virtual core becomes runnable while other threads in the same virtual core are already running in the guest, it is possible for the latecomer to join the others on the core without first pulling them all out of the guest. Currently this only happens rarely, when a vcpu is first started. This fixes some bugs and omissions in the code in this case. First, we need to check for VPA updates for the latecomer and make a DTL entry for it. Secondly, if it comes along while the master vcpu is doing a VPA update, we don't need to do anything since the master will pick it up in kvmppc_run_core. To handle this correctly we introduce a new vcore state, VCORE_STARTING. Thirdly, there is a race because we currently clear the hardware thread's hwthread_req before waiting to see it get to nap. A latecomer thread could have its hwthread_req cleared before it gets to test it, and therefore never increment the nap_count, leading to messages about wait_for_nap timeouts. Signed-off-by: Paul Mackerras Signed-off-by: Alexander Graf --- arch/powerpc/include/asm/kvm_host.h | 7 ++++--- arch/powerpc/kvm/book3s_hv.c | 14 +++++++++++--- 2 files changed, 15 insertions(+), 6 deletions(-) diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h index 68f5a308737a..218534d46ae9 100644 --- a/arch/powerpc/include/asm/kvm_host.h +++ b/arch/powerpc/include/asm/kvm_host.h @@ -289,9 +289,10 @@ struct kvmppc_vcore { /* Values for vcore_state */ #define VCORE_INACTIVE 0 -#define VCORE_RUNNING 1 -#define VCORE_EXITING 2 -#define VCORE_SLEEPING 3 +#define VCORE_SLEEPING 1 +#define VCORE_STARTING 2 +#define VCORE_RUNNING 3 +#define VCORE_EXITING 4 /* * Struct used to manage memory for a virtual processor area diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c index 3a737a4bb8bf..89995fa6e945 100644 --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -336,6 +336,11 @@ static void kvmppc_update_vpa(struct kvm_vcpu *vcpu, struct kvmppc_vpa *vpap) static void kvmppc_update_vpas(struct kvm_vcpu *vcpu) { + if (!(vcpu->arch.vpa.update_pending || + vcpu->arch.slb_shadow.update_pending || + vcpu->arch.dtl.update_pending)) + return; + spin_lock(&vcpu->arch.vpa_update_lock); if (vcpu->arch.vpa.update_pending) { kvmppc_update_vpa(vcpu, &vcpu->arch.vpa); @@ -1009,7 +1014,7 @@ static void kvmppc_run_core(struct kvmppc_vcore *vc) vc->n_woken = 0; vc->nap_count = 0; vc->entry_exit_count = 0; - vc->vcore_state = VCORE_RUNNING; + vc->vcore_state = VCORE_STARTING; vc->in_guest = 0; vc->napping_threads = 0; @@ -1062,6 +1067,7 @@ static void kvmppc_run_core(struct kvmppc_vcore *vc) kvmppc_create_dtl_entry(vcpu, vc); } + vc->vcore_state = VCORE_RUNNING; preempt_disable(); spin_unlock(&vc->lock); @@ -1070,8 +1076,6 @@ static void kvmppc_run_core(struct kvmppc_vcore *vc) srcu_idx = srcu_read_lock(&vcpu0->kvm->srcu); __kvmppc_vcore_entry(NULL, vcpu0); - for (i = 0; i < threads_per_core; ++i) - kvmppc_release_hwthread(vc->pcpu + i); spin_lock(&vc->lock); /* disable sending of IPIs on virtual external irqs */ @@ -1080,6 +1084,8 @@ static void kvmppc_run_core(struct kvmppc_vcore *vc) /* wait for secondary threads to finish writing their state to memory */ if (vc->nap_count < vc->n_woken) kvmppc_wait_for_nap(vc); + for (i = 0; i < threads_per_core; ++i) + kvmppc_release_hwthread(vc->pcpu + i); /* prevent other vcpu threads from doing kvmppc_start_thread() now */ vc->vcore_state = VCORE_EXITING; spin_unlock(&vc->lock); @@ -1170,6 +1176,7 @@ static int kvmppc_run_vcpu(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu) kvm_run->exit_reason = 0; vcpu->arch.ret = RESUME_GUEST; vcpu->arch.trap = 0; + kvmppc_update_vpas(vcpu); /* * Synchronize with other threads in this virtual core @@ -1193,6 +1200,7 @@ static int kvmppc_run_vcpu(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu) if (vc->vcore_state == VCORE_RUNNING && VCORE_EXIT_COUNT(vc) == 0) { vcpu->arch.ptid = vc->n_runnable - 1; + kvmppc_create_dtl_entry(vcpu, vc); kvmppc_start_thread(vcpu); } -- 2.20.1